Synergistic enhancement of apoptosis by DNA- and cytoskeleton-damaging agents: a basis for combination chemotherapy of cancer

Actinomycin D (AD)-induced apoptosis in CMK-7 cells is greatly accelerated by cytoskeletal poisons such as colcemid (CL) and cytochalasin D (CD). This phenomenon is important in the combination chemotherapy of cancer so that its generality was investigated. Four human leukemia and two human solid tumor cell lines were treated with combinations of one DNA-damaging agent [AD, mitomycin C (MMC), or etoposide (VP- 16)] and one cytoskeletal poison [CL, CD, or vinblastine (VBL)]. The apoptosis was monitored by assaying caspase-3 activity and the DNA cleavage ratio. The caspase-3 activation in all leukemia and HeLa S3 cell lines was, except for a few cases, 1.3-to 6.0-fold enhanced by combinations of the DNA-damaging agent with a cytoskeletal poison. The DNA cleavage ratio as well as the dead cell ratio was also 1.4-to 23.7-fold enhanced in CMK-7, U-937, HeLa S3, and Colo320 DM cell lines by the combinations of AD with CL, CD, or VBL. The combination index for caspase-3 activation by AD and CL in U-937 cells was smaller than 1 at Fa of more than 0.03. Thus, apoptosis in many tumor cell lines is synergistically enhanced by various combinations of DNA- and cytoskeleton-damaging agents.

Chemokine receptor 1 knockout abrogates natural killer cell recruitment and impairs type-1 cytokines in lymphoid tissue during pulmonary granuloma formation

Mice with targeted mutation of chemokine receptor 1 (CCR1) were used to assess the contribution of CCR1 agonists to local, regional, and systemic inflammatory-related events during experimental pulmonary granuloma formation. Models of Th1 (type-1) and Th2 (type-2) cell-mediated lung granulomas were induced in wild-type (CCR+/+) and knockout (CCR1-/-) mice by embolizing Sepharose beads coupled to the purified protein derivative of Mycobacterium bovis or soluble antigens derived from Schistosoma mansoni eggs. Morphometric analysis indicated that granuloma sizes were unchanged in CCR1-/- mice, but flow cytometric analyses of dispersed granulomas revealed that natural killer cell recruitment to type-1 lesions was abrogated by 60%. Analysis of cytokine production by draining lymph node cultures showed altered expression in CCR1-/- mice characterized by reduced interleukin-2 and interferon-gamma in the type-1 response, and enhanced interleukin-5 and interleukin-13 in the type-2 response. Peripheral blood leukocytosis was also enhanced in the type-1 but not the type-2 response. These findings suggest that CCR1 agonists contribute to multiple immunoinflammatory events in the type-1 granulomatous response with natural killer cell accumulation being particularly sensitive to CCR1 disruption. Although functional efficacy of granulomas may be altered, chemokine redundancy and cytokine reserve seem to make the bulk of the exudative response resistant to CCR1 disruption.

Cytoskeletal disruption accelerates caspase-3 activation and alters the intracellular membrane reorganization in DNA damage-induced apoptosis

In actinomycin D (AD)-induced apoptosis, caspase-3 activation and DNA cleavage in human megakaryoblastic leukemia CMK-7 cells were greatly accelerated by tubulin and actin polymerization inhibitors [e.g., colcemid (CL) and cytochalasin D (CD), respectively], but the acceleration was not found with Taxol or phalloidin. A decrease in mitochondrial transmembrane potential, release of cytochrome c into the cytosol, and cleavage of procaspase-9 to its active form preceded the activation of caspase-3 and, moreover, all of these events began earlier and/or proceeded faster in cells treated with AD plus CL or CD than in cells treated with AD only. These results suggest that cytoskeletal disruption in the apoptotic cells promotes damage of the mitochondrial membrane, resulting in the enhanced release of cytochrome c necessary for the activation of caspase-9 that initiates the caspase cascade. On the other hand, apoptotic bodies were rapidly formed from cells treated with AD and CL, but were suppressed when treated with AD and CD. Intracellular membranes and the actin system were reorganized to surround the nuclear fragments in the AD- and CL-treated cells, but such a membrane system was not formed in the presence of CD, implying that the apoptotic bodies are formed via reorganization of intracellular membranes under regulation by actin polymerization. Thus, the cytoskeletal change in CMK-7 cells has a strong effect on the early biochemical process as well as on the later morphologic process in AD-induced apoptosis.

Interleukin 4 and 13 participation in mycobacterial (type-1) and schistosomal (type-2) antigen-elicited pulmonary granuloma formation: multiparameter analysis of cellular recruitment, chemokine expression and cytokine networks

The contribution of IL-4 and IL-13 to inflammation and cytokine responses was compared in mice with types-1 or -2 pulmonary granulomas (GR) elicited by beads bound to antigens of Mycobacteria bovis (PPD) or Schistosoma mansoni eggs (SEA). Type-2 SEA-GR produced the most IL-4 and IL-13. Type-1 PPD-GR produced detectable IL-13, but not IL-4. Mice were treated with anti-IL4 or anti-IL-13 Abs, then lesion size/composition, cytokine/chemokine mRNA and lymph node cytokines were measured. Type-1 GRs resisted individual Abs, but combined Abs augmented lesions by 20%. In contrast, anti-IL-4 abrogated type-2 GR by 30-40% and eosinophil recruitment by 60%. Anti-IL-13 abrogated type-2 GR by 20-30% with no effect on eosinophils. Combined depletion reduced lesion area by 60% and eosinophils by more than 80%. In type-1 GR lungs, anti-IL-4 and anti-IL-13 augmented IFNgamma and TNFalpha mRNA. In type 2 lungs, anti-IL-13 did likewise, but anti-IL-4 decreased TNFalpha without affecting IFNgamma mRNA. In both responses, IL-4 promoted MCP-1 and MCP-5 mRNA, but IL-13 inhibited chemokines in type-1 GR. In lymph nodes, anti-IL-4, but not anti-IL-13, abrogated type-2 cytokines. In fact, IL-13 down-regulated itself and other type-2 cytokines. In summary, IL-4 and IL-13 have common and disparate regulatory functions in types 1 and 2 responses.

The controlled introduction of multiple negative charge at single amino acid sites in subtilisin Bacillus lentus

The use of methanethiosulfonates as thiol-specific modifying reagents in the strategy of combined site-directed mutagenesis and chemical modification allows virtually unlimited opportunities for creating new protein surface environments. As a consequence of our interest in electrostatic manipulation as a means of tailoring enzyme activity and specificity, we have adopted this approach for the controlled incorporation of multiple negative charges at single sites in the representative serine protease, subtilisin Bacillus lentus (SBL). A series of mono-, di- and triacidic acid methanethiosulfonates were synthesized and used to modify cysteine mutants of SBL at positions 62 in the S2 site, 156 and 166 in the S1 site and 217 in the S1' site. Kinetic parameters for these chemically modified mutant (CMM) enzymes were determined at pH 8.6 under conditions which ensured complete ionization of the unnatural amino acid side-chains introduced. The presence of up to three negative charges in the S1, S1' and S2 subsites of SBL resulted in up to 11-fold lowered activity, possibly due to interference with oxyanion stabilization of the transition state of the hydrolytic reactions catalyzed. Each unit increase in negative charge resulted in a raising of K(M) and a reduction of k(cat). However, no upper limit was observed for increases in K(M), whereas decreases in k(cat) reached a limiting value. Comparison with sterically similar but uncharged CMMs revealed that electrostatic effects of negative charges at positions 62, 156 and 217 are detrimental, but are beneficial at position 166. These results indicate that the ground-state binding of SBL to the standard substrate, Suc-AAPF-pNA, to SBL is reduced, but without drastic attenuation of catalytic efficiency, and show that SBL tolerates high levels of charge at single sites.

Toward tailoring the specificity of the S1 pocket of subtilisin B. lentus: chemical modification of mutant enzymes as a strategy for removing specificity limitations

In both protein chemistry studies and organic synthesis applications, it is desirable to have available a toolbox of inexpensive proteases with high selectivity and diverse substrate preferences. Toward this goal, we have generated a series of chemically modified mutant enzymes (CMMs) of subtilisin B. lentus (SBL) possessing expanded S(1) pocket specificity. Wild-type SBL shows a marked preference for substrates with large hydrophobic P(1) residues, such as the large Phe P(1) residue of the standard suc-AAPF-pNA substrate. To confer more universal P(1) specificity on S(1), a strategy of chemical modification in combination with site-directed mutagenesis was applied. For example, WT-SBL does not readily accept small uncharged P(1) residues such as the -CH(3) side chain of alanine. Accordingly, with a view to creating a S(1) pocket that would be of reduced volume providing a better fit for small P(1) side chains, a large cyclohexyl group was introduced by the CMM approach at position S166C with the aim of partially filling up the S(1) pocket. The S166C-S-CH(2)-c-C(6)H(11) CMM thus created showed a 2-fold improvement in k(cat)/K(M) with the suc-AAPA-pNA substrate and a 51-fold improvement in suc-AAPA-pNA/suc-AAPF-pNA selectivity relative to WT-SBL. Furthermore, WT-SBL does not readily accept positively or negatively charged P(1) residues. Therefore, to improve SBL's specificity toward positively and negatively charged P(1) residues, we applied the CMM methodology to introduce complementary negatively and positively charged groups, respectively, at position S166C in S(1). A series of mono-, di-, and trinegatively charged CMMs were generated and all showed improved k(cat)/K(M)s with the positively charged P(1) residue containing substrate, suc-AAPR-pNA. Furthermore, virtually arithmetic improvements in k(cat)/K(M) were exhibited with increasing number of negative charges on the S166C-R side chain. These increases culminated in a 9-fold improvement in k(cat)/K(M) for the suc-AAPR-pNA substrate and a 61-fold improvement in suc-AAPR-pNA/suc-AAPF-pNA selectivity compared to WT-SBL for the trinegatively charged S166C-S-CH(2)CH(2)C(COO(-))(3) CMM. Conversely, the positively charged S166C-S-CH(2)CH(2)NH(3)(+) CMM generated showed a 19-fold improvement in k(cat)/K(M) for the suc-AAPE-pNA substrate and a 54-fold improvement in suc-AAPE-pNA/suc-AAPF-pNA selectivity relative to WT-SBL.

Application of recombinant human granulocyte colony stimulating factor in children with acute myeloid leukemia

OBJECTIVE

To evaluate the effect of recombinant human granulocyte colony stimulating factor (rhG-CSF) on accelerating neutrophil recovery and decrease fatal infections for childhood acute myeloid leukemia (AML).

METHODS

From November 1992 to March 1997, 45 patients were enrolled into our study and 15 were newly diagnosed. All were treated with high dose chemotherapy combined with rhG-CSF.

RESULTS

Of 15 newly diagnosed patients, 13 achieved complete remission (CR) after one course of therapy and 2 achieved CR after two courses of therapy. For newly diagnosed patients, the durations of absolute neutrophil counts (ANC) < 0.5 x 10(9)/L were 5 days and 10 days in rhG-CSF group and control group respectively (P < 0.05). The incidences of infection of these two groups were 40% and 60% respectively (P < 0.05). As for patients who received intensive therapy, the durations of ANC < 0.5 x 10(9)/L were 5 days and 8 days in rhG-CSF group and control group, respectively (P < 0.05), and the incidences of infection were 25% and 44.4% respectively (P < 0.05).

CONCLUSIONS

The application of rhG-CSF in children with AML after chemotherapy may hasten the hematopoietic recovery. The duration of neutropenia was shortened by 3-4 days, and the incidence of fatal infection was reduced. rhG-CSF does not stimulate AML growth in vivo.

A combinatorial approach to chemical modification of subtilisin Bacillus lentus

The reaction between methanethiosulfonate reagents and cysteine mutants of subtilisin is quantitative and can be used to prepare chemically modified mutant enzymes (CMMs) with novel properties. The virtually unrestricted structural variations possible for CMMs presents a preparative and screening challenge. To address this, a rapid combinatorial method for preparing and screening the activities of CMMs has been developed.

[The relationship between p53 mutation and esophageal cancer biological behavior]

OBJECTIVE

To investigate the relationship between p53 mutation and esophageal cancer biological behavior as well as its prognostic role in esophageal cancer.

METHOD

Mutations in exon 5-8 of p53 were screened in 30 sporadic esophageal cancers by a combination of PCR-SSCP and PCR-direct DNA silver sequencing.

RESULTS

Mutations were found in 11 cases (36.7%). There were 9 point mutations, including 4 missense mutations, 2 nonsense mutations, 3 silent mutations. The other 2 cases were frameshift mutations due to base insertion and deletion. With statistical analysis, the p53 mutation rate was 56.3% in moderately and poorly-differentiated esophageal cancers, 14.3% in well-differentiated cases, with a highly significant difference between the two groups (P=0.025). The mutation rate of the cancers with all layers invaded (52.6%) was remarkably higher than that of the cancers without all layers invaded (9.1%)(P=0.024). A significantly higher rate of p53 mutation was also seen in cases with lymph nodes metastasis (61.5%) than in cases with no lymph nodes metastasis (17.6%) (P=0.024).

CONCLUSION

The data suggest that there is a strong correlation between the presence of p53 mutation and the biological behavior of human esophageal cancer, such as histologic differentiation, invasion stage, and regional lymph nodes metastasis. Detection of p53 mutation can be helpful in identifying more progressive esophageal cancer and assessing prognosis. The study also discussed the dominant negative effect of p53 and the genetic effect of silent mutation.

[The effect of Rhodiola capsules on oxygen consumption of myocardium and coronary artery blood flow in dogs]

It has been proved that Rhodiola Capsules can obviously decrease the oxygen consumption of myocardium and oxygen consumption index in anesthetic dogs, decrease the coronary artery resistance, but have no marked effect on the coronary artery blood flow. The Capsules also have the function of decreasing blood presure and slowing heart rate.

In vitro selection and regeneration of cotton resistant to high temperature stress

Cell suspension cultures of cotton (Gossypium hitirsutum L. cv. Coker 312) were exposed to various temperature:time treatments in order to select cell lines resistant to high temperature stress. Cells were exposed to 45°C for 3 h each day until the total accumulated hours of stress were: 0 h, 10 h, 75 h, 100 h, or 105 h (81 h pulsed then 24 h continuous). After the stress treatments, the cells were plated onto embryo development medium and plants were recovered. The embryogenic calli that were recovered were subcultured monthly for 6 months and tested for increased resistance to the temperature:time treatments previously determined to be lethal and to water stress as imposed by PEG. All of the selected cell lines were more resistant to both types of stress than the control cell lines. Leaf tissue of stress selected (Ro) formed and maintained callus growth when incubated at 38°C; whereas, tissue excised from nonselected controls rarely formed callus and calli which did form quickly became necrotic. These cells and plants will provide a tool for determining the mechanisms involved in resistance to high temperature stress.